Emergence of KPC-134, a KPC-2 variant associated with ceftazidime-avibactam resistance in a ST11 Klebsiella pneumoniae clinical strain

The emergence of various new Klebsiella pneumoniae carbapenemase (KPC) variants leading to ceftazidime-avibactam treatment failure is a new challenge in current clinical anti-infection treatment. Here, we report a ceftazidime-avibactam-resistant K. pneumoniae 1072-2 clinical strain carrying a novel KPC variant, KPC-134, which differs from KPC-2 by both single mutation (D178A) and 8-amino acid insertions (asp-asp-asn-arg-ala-pro-asn-lys). The results of antimicrobial susceptibility testing showed that the isolate was resistant to meropenem (MIC = 4 mg/L), ceftazidime (MIC >= 32 mg/L), cefepime (MIC >= 128 mg/L), aztreonam (MIC >= 128 mg/L), and ceftazidime-avibactam (MIC >= 128 mg/L) but sensitive to imipenem (MIC = 0.5 mg/L), imepenem-relebactam (MIC = 0.5 mg/L), meropenem-vaborbactam (MIC = 2 mg/L), and aztreonam-avibactam (MIC = 4 mg/L). The plasmid containing bla(KPC-134) was isolated from K. pneumoniae, and the bla(KPC-134) gene was cloned into plasmid pHSG398 and transformed into an Escherichia coli DH5 alpha to observe changes in antimicrobial resistance. The results indicated that the transformant was positive for bla(KPC-134) and increased MICs of ceftazidime-avibactam, ceftazidime, cefepime, and aztreonam by 512-fold, 256-fold, 16-fold, and 4-fold, respectively, compared with the recipient. The results of third-generation sequencing showed that the bla(KPC-134) gene was carried by a 133,789 bp IncFII-IncR plasmid, and many common resistance genes (including bla(CTX-M-65), bla(TEM-1B), bla(SHV-12), rmtB, and catB4) along with the IS26, tnpR, ISkpn8, ISkpn6-like, and Tn1721 elements were identified. IMPORTANCE The emergence of various new KPC variants leading to ceftazidime-avibactam treatment failure is a new challenge for clinical anti-infection treatment. Here, we describe the characterization of a ceftazidime-avibactam-resistant blaKPC-134-positive Klebsiella pneumoniae clinical strain for the first time. K. pneumoniae bearing with KPC variant often mislead clinical anti-infection treatment because of their unique antimicrobial susceptibility profile and the tendency of conventional carbapenemase assays to give false negative results. Therefore, timely identification of KPC variants and effective anti-infective therapy are key to saving infected patients.